Twenty-four cultivars of Malus spp. were evaluated for resistance to naturally occurring insect pests at replicated plantings in Detroit, Lansing, and Cadillac, Michigan. ‘Adams,’ ‘Candied Apple,’ and ‘Sugar Tyme’ crabapples were the most resistant to defoliation by gypsy moth, fall cankerworm, and eastern tent caterpillar. ‘Sugar Tyme,’ in particular, was almost untouched by gypsy moth or fall cankerworm (less than 1.3% defoliation). These data must be interpreted cautiously, because previous research has shown that gypsy moth larvae are attracted to the largest Malus trees in a planting, regardless of cultivar.
Two cultivars, ‘Robinson’ and ‘Red Jewel,’ were highly resistant to rose chafer and apple-and-thom skeletonizer damage. The fact that neither of these were particularly resistant to gypsy moth or cankerworm suggests a different mechanism of resistance for defoliators and skeletonizers.
2Associate Professors of Entomology and Horticulture, respectively. We appreciate the efforts of Jan Eschbach in preparing this manuscript, and Terrance Davis for coordinating the field research. This research was partially supported by a grant from the Horticultural Research Institute, 1250 I Street N.W., Suite 500, Washington, DC 20005, and the Michigan Agricultural Experiment Station, East Lansing, MI 48824.